Bandwidth demand on telecommunications networks is increasing. In response, the International Telecommunication Union (ITU) has standardized optical transport networks (OTN), which is a dense wavelength division multiplexing (DWDM) network. The rates and formats of OTN constructs such as optical channel transport unit (OTUk) and optical channel data unit (ODUk) are defined in ITU Telecommunication Standardization Sector (ITU-T) recommendation G.709.
The ITU-T recommendation G.709 has a defined number of ODUk frames, for example, k=0, 1, 2, 2e, 3 and 4, in order of increasing rates. A lower rate ODUj can be multiplexed into a higher rate ODUk. Multi-level multiplexing is permitted under the recommendation. For example, four ODU1 streams may be multiplexed into an ODU2, which may, in turn, be multiplexed along with nine other ODU2 streams, into an ODU4.
In a conventional OTN network element (NE) with a single shelf, there may be 16 to 20 linecards. In a multi-shelf NE, there may be up to 128 linecards. Within each linecard, there may be up to 2 levels of ODTUjk multiplexing, resulting in up to three levels ODUk termination sources and sinks. For an OTU4 linecard, there may be up to 121 ODUk termination sources and sinks. A multi-shelf NE can, therefore, contain up to 128*121=15488 ODUk termination sources and sinks. It may be possible for each linecard to terminate multiple OTU4's or the yet to be defined OTU5.
For backward defect indication (BDI) and backward error indication (BEI) reporting, each ODUk termination source is associated with two ODUk termination sinks. One of the sinks is assumed to be located at the local linecard. The other sink may be located in a remote linecard. It is desirable to provide an efficient method to do the many-to-many connection between the ODUk termination sinks and the corresponding ODUk termination source.
For automatic protection switching (APS) events, due to the tight time budget to respond to events, overheads need to be piped to the APS controller to do the appropriate working and protect switch over and communication links. It is desirable to provide an economical solution for piping the OTN overhead and defects to the APS controller.